In a person without diabetes, several systems including, for example, the metabolic, endocrine, and cardiovascular systems, function collectively to maintain homeostasis. However in a person with diabetes, the inherent glucose regulation mechanism is dysfunctional. Glucose levels are affected by the state of the metabolic-physiological-endocrine system. This includes factors such as insulin, stress, physical activity, hormonal levels, and fatigue. The effects of all these factors on blood glucose concentration (BGC) are highly complex and inter-related. In addition, factors such as food intake can cause glucose levels to change greatly and make glucose regulation and health management more difficult. These various factors are referred to as disturbances.
Insulin therapy involves multiple daily doses of insulin before meals or to correct high blood glucose, with the amount either pre-recommended by a physician or decided by the patient on the basis of measured BGC and the number of carbohydrates they estimate will be ingested at the time of the meal. This protocol is inconvenient and unreliable. It often results in hypoglycemic and/or hyperglycemic episodes, both of which can be life-limiting and life-threatening. Thus, there has been a desire to develop more optimized insulin delivery systems and protocols. This has included research to develop automatic insulin delivery systems.
The potential for successful automatic insulin delivery has entered a new era due to recent technological advancements of insulin pumps and blood glucose sensors. However, for full automation and control capable of reducing the variance in BGC, the control algorithm must be capable of tight control for major disturbances such as meals, activity, and stress. Theoretically, the superiority of feedforward control (FFC) over all other control systems is that corrective action can be taken to cancel the effects of disturbances on the control variable (i.e., BGC) proactively. FFC has not been capable of addressing the complexity of various input disturbances impacting the regulation of blood glucose levels associated with diabetes due to inadequacy of effective model development of the complex causative relationships of disturbances and the controlled variable. This is insufficient as it fails to determine accurately the insulin infusion rate to substantially eliminate the effects of the modeled disturbances.
While Feedback Control (FBC) and some model-based algorithms have shown promise and progress in real studies, there does not appear to be any clinical studies of an FFC or Feedback Feed Forward Control (FBFF) approach on real subjects in the literature. Actually, even from a search in the process control literature the successful implementation of FFC on real systems appears to be quite limited. This is likely due to the difficulty of developing accurate causal relationship of inputs on the controlled variable for real processes because of the existence of unmeasured disturbances and pairwise correlation of the inputs. Therefore, the objective of this work is the development of a subject-specific FFC modeling methodology under free-living data collection to effectively compensate for changes in meals, activity, and stress.
Consequently, there is a significant need for a system providing automatic delivery of insulin with minimal variability around the desired glucose target.
Accordingly, it is an objective of the claimed invention to provide a semi-coupled modeling network that presents a more phenomenological FFC law that includes input dynamics, unmeasured pseudo-blood insulin and blood glucose dynamics and blood glucose levels.
Other objects, advantages and features of the present invention will become apparent from the following specification taken in conjunction with the accompanying drawings.
While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.